During one of the mind-numbing arguments between the candidates, Sen.Barack Obama (D-Ill.) was fighting off the claim that his universal healthcare proposal might not cover up to 15 million Americans. As an academic issue, it was an important exchange. But I suddenly realized: In real-world terms, the back-and-forth didn't much matter.

In this epic race for the Democratic nomination, the most minute policy differences are extrapolated into bombastic TV ads, direct mail pieces and debate one-liners. Amid the noise, few remember that what candidates say or propose can bear little resemblance to what ends up happening once they are in the Oval Office.

As proof, look no further than candidate Bill Clinton who said, "I'd be for, but only if it lifted their wage rates and their labor standards and they cleaned up their environment so we could both go up together instead of being dragged down." And yet, he subsequently steamrolled NAFTA through Congress.

Of course, every presidential election is, in that way, a leap of faith. But we can make an educated guess about what the different candidates' relationship to Congress will likely be, and that relationship dictates the possibilities for progress far more than any campaign promises. For example, in 2000 and 2004, a vote for Bush was a vote to centralize more government power in the hands of the White House, and, just as importantly, to create a rubber stamp for an extremist Republican Congress.

With Bush vetoing the fewest bills of any president since the Civil War, movement conservatives were emboldened by the Bush administration to wield as much raw legislative power as the president himself.

For voters trying to distinguish between Sen. Hillary Clinton (D-N.Y.) and Obama, the question should be who is more apt to empower a Democratic Congress whose seniority and power rests in the hands of committed progressives.

**Seniority and ideology**

A look across the committee structure on Capitol Hill highlights a unique opportunity for exponential change under a Democratic president. In the House, progressives are concentrated in two clusters: New members swept in by the recent wave of anti-Bush sentiment, and senior lawmakers elected in the more progressive, pre-Reagan era.

Liberal Reps. David Obey (D-Wis.) and Charles Rangel (D-N.Y.) chair the two most powerful panels in Congress: the House Appropriations Committee, which oversees federal spending, and the Ways and Means Committee, which oversees taxes. Another liberal, Rep. George Miller (D-Calif.), heads the Education and Workforce Committee that will be charged with reforming No Child Left Behind and strengthening labor laws. And progressive stalwart Rep. John Conyers (D-Mich.) heads the Judiciary Committee that could reform or scrap the Patriot Act.

In the Senate, the situation is much the same. Though many mid-level members of the Democratic caucus are rooted in the mealy-mouthed politics of mid-'90s Clintonism, progressive backbone is found among freshman populists like Sen. Sherrod Brown (D-Ohio) and, more importantly, among committee chairs like Sens. Barbara Boxer(D-Calif.), Ted Kennedy (D-Mass.) and Pat Leahy (D-Vt.). These three, respectively, run the Senate's Environment and Public Works Committee overseeing climate change legislation; the Health, Education, Labor and Pensions Committee involved in most domestic policies; and the Judiciary Committee impacting both civil liberties and nominations to the federal bench.

The less these progressives are inhibited by the executive branch and the threat of presidential vetoes, the more progressive change will come from Washington. In other words, the more Ted Kennedy is allowed to be Ted Kennedy, the better.

**Clinton: "hands-on"**

Clinton has promised to be a "hands-on" president and criticized Obama for being vague about his policy prescriptions, a sure fire sign that her administration would mean heavy executive branch influence over Congress. As political theorist James David Barber might say, Clinton would be an "active" archetype, involved in the most granular details of the legislative process.

In and of itself, this is not a negative. Passing some of American history's most important legislation has required such presidential engagement, from the New Deal program of Franklin Delano Roosevelt to the landmark bills of the '60s shepherded through Congress by Lyndon Johnson.

A domineering executive branch under Clinton, however, poses a potential problem, best summed up by one word: triangulation. The first Clinton administration would position itself against Democrats in Congress when it believed doing so was politically opportune. In a Republican Congress, such triangulation meant the Clinton White House worked with the right to pass initiatives like NAFTA and welfare reform, to name just two.

In a Democratic Congress today, triangulation could mean stopping the passage of progressive legislation, with a President Hillary Clinton vetoing bills as a way to burnish her so-called "centrist" credentials. Couple Clintonism's ideological affinity for triangulation with Hillary Clinton's public defense of corporate lobbyists, and the perils come into full relief. It would be no stretch to imagine a Democratic Congress passing some form of single-payer universal healthcare measure, only to have it crushed by a triangulating Clinton veto (or veto threat). The plaudits for such "toughness" would come from both the faux "centrists" in the Washington press corps and the health industry that has given more money to Clinton than to any other candidate.

**Obama: Alinsky and lawmaking**

The Nation's Chris Hayes recently wrote that Obama's overarching diagnosis of what 's wrong with politics is the way it is conducted rather than for whom. Put another way, it's not the what but the how. Fix how politics is waged, build a "working majority," as Obama says, and solutions to big problems will come. This is a theme of famed activist Saul Alinsky, whose community organizations Obama worked with as a young man in Chicago. As Alinsky wrote in Rules for Radicals, the best organizers possess a belief that if people have the power to act in the long run, they will, most of the time, reach the right decisions. A President Obama would probably apply such a principle to Congress.

Thanks to Obama's nonconfrontational message of hope and unity, he would be elected less with a mandate to enact anything specific than a mandate to get things done. almost irrespective of what those things are.

n James David Barber's terms, Obama would be a more "passive" president, like the one he credited with political acumen: Ronald Reagan. The Gipper spent his political capital outlining overarching themes, and he avoided Capitol Hill brawls. A Democrat in that Reagan mold working with an assertive Democratic Congress clearly has more potential upsides than downsides.

Certainly, Obama has, on occasion, rhetorically triangulated against fellow Democrats. He once appeared on NBC's "Meet the Press" to publicly lambaste proposals to withdraw troops from Iraq. However, his concrete legislative actions (votes, bill sponsorships, etc.) have been solidly progressive, suggesting his general aversion to conflict-charged vetoes would be most pronounced when dealing with progressive legislation. To again cite the healthcare hypothetical, it is easy to imagine a President Obama calling for universal healthcare with certain broad parameters, letting Democratic congressional leaders wage the trench warfare needed to pass it, and then signing a final bill, even if it ended up being more progressive than what he had in mind.

Admittedly, predicting future presidential behavior is all conjecture, and the known qualities of the candidates could produce far different results. Clinton's hands on style could result in a string of legislative victories for progressives that would have been impossible without that leadership style. Likewise, Obama's potential aversion to the veto pen might halt him from obstructing progressive bills, but it may also prevent him from stopping conservative ones that should be blocked. Though the media's obsessive focus on presidential politics may lead us to believe the White House is all-powerful, Congress has been central to most of history's great reforms. That means this race is not just about which candidate appears more progressive, but also about which candidate will allow progressives in Congress to be strongest.